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1983 Z28 rearend problems?

3K views 18 replies 4 participants last post by  Tom' 
#1 ·
Hello. New here I have a 83 z28 the axle codes match for a posi vin mubers too.have read several posts none seem to match my ? I turn wheels by hand other doesn't move at all did have new ring and pinion installed yrs ago. Is it just wore out or could the mechanic have ripped me off and taken my posi unit and put a different unit in. I'm second own .er. Previous never had anything changed .
,can anybody help thanks
 
#6 ·
Can you post a pic?

The '83 would have had the Auburn limited slip differential. When they wear out they stop spinning both tires and at this point they are scrap metal. You can not rebuild them.

Here is something to think about. The 7.5 rear end uses a 2 series differential for 2.14 to 3.08 gears and a 3 series differential for 3.23 to 4.56 gears. If you had a 2 series Auburn and you went to gears in the 3.23 to 4.56 range then the guy who put the gears in might have swapped your 2 series Auburn for a 3 series standard differential so that the gears would fit.
 
#13 · (Edited)
If it's an original 3.73 Auburn rear end then it will have RPO coded GT4 and G80 on the sticker on the bottom of the console lid or on the back of the spare tire cover.

Just looked at the pic and that is a standard differential. If you had an Auburn then it's gone now.

If you decide to put another differential in it I do NOT recommend using another Auburn. They are at the very bottom of my list of good differentials. I would recommend using a Eaton Posi, Eaton Truetrac or a Yukon Dura Grip, depending on what you want to do with the car. I would also recommend upgrading your 26 spline axles to the later 28 spline axles at the same time.
 
#16 ·
You have 2 weak links in the drive train, but as long as you don't abuse it too much it should be fine with street tires. The T5 and the 7.5 rear end can not handle a lot of abuse.

If this car will be built toward street/strip use then the Eaton Posi or Yukon Dura Grip would be a good choice. If it will be built more for street and auto cross/road racing then the Truetrac or Torsen would be a good choice. All of these are available in 3 series with 28 splines. When you make your choice I can recommend a good supplier for the parts.
 
#18 ·
The codes are on a white sticker that is usually on the bottom of the console lid or on the back of the spare tire cover. Yours might be in a different location. If you can find it you will have all of the information about what your car came with, including the engine, transmission, suspension, brakes and other options. The codes are in alphabetical order and the rear end codes start with a G, the engine codes start with a L and the transmission codes start with a M.

Tom's Differentials is a great place to get Eaton parts, installation kits and AAM axles. His prices are good and his parts are among the best. He is kind of a grumpy old fella, so don't take it personal if he isn't cheerful.
 
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